There are a number of conventional processes for packaging integrated circuits. One approach, which is commonly referred to as “flip chip” packaging, generally contemplates forming solder bumps (or other suitable contacts) directly on an integrated circuit die. The die is then “flipped” and attached to a substrate such as a printed circuit board or substrate. The solder bumps on the die are aligned and mounted onto matching contacts on the substrate. The solder bumps are then reflowed to electrically connect the die to the substrate.
When a semiconductor device such as, e.g., a flip chip die is mounted to the substrate, an air gap typically remains between the die and substrate. This gap is commonly filled with material that flows into the gap in liquid form and then solidifies. This material is generally a mixture of an epoxy resin and small silica spheres and is often called underfill. The underfill is typically applied in liquid form from a dispenser at one edge of the die. The underfill then flows into the narrow gap due to capillary action and spreads across the flip chip die until finally the entire area of the gap between the die and substrate is filled.
A number of problems are associated with this underfill process. For example, the operation of applying underfill must be repeated for each flip chip mounted onto a substrate. Repeating such an operation many times during manufacturing significantly increases costs and limits manufacturing throughput. Additional challenges may be presented in methods that entail the underfill being dispensed with a needle along one side of each die. Capillary action draws the dispensed underfill underneath the die. However, flow of the underfill is difficult to control and may result in defects. For example, underfill flow between adjacent die may result in the formation of voids or non-uniform underfill density beneath the IC dice. These defects may induce stress due to uneven thermal expansion. Sufficient spacing is provided between adjacent dice to provide room for a needle to dispense the underfill along at least one edge of each die as well as to prevent uncontrolled flow of underfill between adjacent dice.
One or more embodiments of the present invention may address one or more of the above issues.